Image transmission device, image transmission method, image reception device, and image reception method

ABSTRACT

In prior art documents, no consideration is given as to how to more faithfully preserve image (here and subsequently also termed “video”) data of larger size during transmission. Provided is an image transmission device for transmission of image data, characterized by having a compression processor for compressing image data, and an output section for outputting compressed data having been compressed by the compression processor, the output section outputting the compressed data separately during a first interval and a second interval different from the first interval.

TECHNICAL FIELD

The technical field relates to transmission and reception of imageinformation.

BACKGROUND ART

In recent times, the number of pixels handled by digital imageprocessing is increasing from year to year in connection with theadoption of 4k2k (3840×2160 pixels) for displays for general users, HD(High Definition: 1920×1080 pixels) for broadcasting and high pixelcapacities for image sensors and displays of digital video cameras.

Regarding formulas of transmitting such image data between equipmentunits, there are the HDMI (High-Definition Multimedia Interface(registered trademark of HDMI Licensing, LLC) standards and DisplayPort(registered trademark or trademark of VESA) standards formulated by VESA(Video Electronics Standards Association).

Regarding the aforementioned HDMI data transmission formula, PatentLiterature 1 states that it is “to selectively transmit uncompressedimage signals or compressed image signals obtained by subjecting theseuncompressed image signals to compression processing by a compressionformula compatible with the receiver device, and permits satisfactorytransmission of image signals at a desired bit rate within thetransmission bit rate range of the transmission path” (see [0048] inPatent Literature 1) and, regarding the compression formula, “the datacompressors 121-1 to 121-n process compression, at a prescribedcompression rate, of uncompressed image signals outputted from the codec117 and outputs compressed image signals. The data compressors 121-1 to121-n constitute an image signal compressing unit. Each of the datacompressors 121-1 to 121-n processes data compression by a differentcompression formula from all the others. For instance, it is statedthat, as compression formulas, “‘RLE (Run Length Encoding)’, ‘Wavelet’,‘SBM (Super Bit Mapping (trademark of Sony))’, ‘LLVC (Low Latency VideoCodec)’, ‘ZIP’ and so forth are conceivable” (see [0077] in PatentLiterature 1).

Further in HDMI, data transmission formats of TMDS (registered trademarkof Transition Minimized Differential Signaling (Silicon Image, Inc.))are used for image data, and Patent Literature 2 is cited as oneexample.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Laid-Open No.2009-213110

Patent Literature 2: Japanese Unexamined Patent Application Publication(Translation of PCT Application) No. 2005-514873

Technical Problem

However, in any of the cited prior literature, no consideration is givento transmissions of images (sometimes referred to as “pictures”; thesame applies hereinafter) of larger sizes while keeping the data morefaithfully.

Solution to Problem

To solve the problem noted above, for instance configurations describedin the Claims are used.

Advantageous Effects of Invention

Whereas the present application covers a plurality of means to solve theproblem, according to one example of the means, there is provided animage transmission device that transmits image data including acompression processor that compresses image data and an output sectionthat outputs compressed image data compressed by the compressionprocessor, wherein the output section outputs the compressed image datadivided between a first period and a second period different from thefirst period.

To cite another example, an image transmission device that transmitsimage data includes a compression processor that processes compressionof image data including a plurality of components, and a datatransmission section that outputs the compressed image data, wherein thedata transmission section alters the outputting method of image data onthe basis of the individual components of the image data.

To cite still another example, an image transmission device thattransmits image data includes a compression processor that processescompression of image data and generates compressed image data andcompression coding information concerning the compression processing,and a data transmission section that outputs compressed image data andthe compression coding information, wherein the redundancy of thecompression coding information is greater than the redundancy of thecompressed image data.

To cite yet another example, an image transmission device that transmitsimage data includes a compression processor that processes compressionof image data and an compressed by the compression processor, whereinthe output section outputs the compressed image data divided between afirst period and a second period different from the first period, andthe compression processor alters, on the basis of the transmission errorrate on a transmission path, compression processing of the image data.

By the means described above, it is made possible to transmission imagedata of a greater size while keeping the data more faithfully.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows one example each of an image transmission device and animage receiving device of a first embodiment.

FIG. 2 shows one example of valid/blanking period of the image data inthe first embodiment.

FIG. 3 shows one example of units of image data to be compressed in thefirst embodiment.

FIG. 4 shows another example of units of image data to be compressed inthe first embodiment.

FIG. 5 shows one example of composition of main compression codinginformation, auxiliary compression coding information and compressedimage data in the first embodiment.

FIG. 6 shows one example of data transmission timing in the firstembodiment.

FIG. 7 shows one example of compression processor in the firstembodiment.

FIG. 8 shows another example of compression processor in the firstembodiment.

FIG. 9 shows another example of compression processor in the firstembodiment.

FIG. 10 shows one example of compressor A in the first embodiment.

FIG. 11 shows one example of compressor A in the first embodiment.

FIG. 12 shows one example of error correction code generator in thefirst embodiment.

FIG. 13 shows one example of data transmission section in the firstembodiment.

FIG. 14 shows one example of header of a compression coding informationpacket in the first embodiment.

FIG. 15 shows one example of data of the compression coding informationpacket in the first embodiment.

FIG. 16 shows another example of header of the compression codinginformation packet in the first embodiment.

FIG. 17 shows another example of data of the compression codinginformation packet in the first embodiment.

FIG. 18 shows one example of compression coding information packet inthe first embodiment.

FIG. 19 shows one example of EDID statement of the image receivingdevice in the first embodiment.

FIG. 20 shows one example of data reception processor in the firstembodiment.

FIG. 21 shows one example of expansion processor in the firstembodiment.

FIG. 22 shows another example of expansion processor in the firstembodiment.

FIG. 23 shows another example of expansion processor in the firstembodiment.

FIG. 24 shows another example of expansion processor in the firstembodiment.

FIG. 25 shows one example of data transmission timing in the firstembodiment.

FIG. 26 shows another example of data transmission timing in the firstembodiment.

FIG. 27 shows one example of compression coding information in the firstembodiment.

FIG. 28 shows another example of compression coding information in thefirst embodiment.

FIG. 29 shows one example of waveform of a serializer in a secondembodiment.

FIG. 30 shows one example of data composition of the serializer outputin the second embodiment.

FIG. 31 shows one example of packet composition of audio data in thesecond embodiment.

FIG. 32 shows one example of bit allocation to various components ofcompressed image data on a transmission path in the second embodiment.

FIG. 33 shows another example of bit allocation to various components ofcompressed image data on a transmission path in the second embodiment.

FIG. 34 shows another example of bit allocation to various components ofcompressed image data on the transmission path in the second embodiment,

FIG. 35 shows another example of bit allocation to various components ofcompressed image data on the transmission path in the second embodiment.

FIG. 36 shows another example of bit allocation to various components ofcompressed image data on the transmission path in the second embodiment.

FIG. 37 shows another example of bit allocation to various components ofcompressed image data on the transmission path in the second embodiment.

FIG. 38 shows another example of bit allocation to various components ofcompressed image data on the transmission path in the second embodiment.

FIG. 39 shows one example of data composition of main compression codinginformation in a third embodiment when no redundancy level is added.

FIG. 40 shows one example of data composition of main compression codinginformation in the third embodiment when a redundancy level is added.

FIG. 41 shows another example of data composition of main compressioncoding information in the third embodiment when the redundancy level isadded.

FIG. 42 shows another example of data composition of main compressioncoding information in the third embodiment when the redundancy level isadded.

FIG. 43 shows one example of data composition of auxiliary compressioncoding information in the third embodiment when the redundancy level isadded.

FIG. 44 shows one example of allocation of compression rate, horizontalblanking period and redundancy level relative to the transmission errorrate in a fourth embodiment.

FIG. 45 shows another example of allocation of compression rate,horizontal blanking period and redundancy level relative to thetransmission error rate in the fourth embodiment.

FIG. 46 shows another example of allocation of compression rate,horizontal blanking period and redundancy level relative to thetransmission error rate in the fourth embodiment.

FIG. 47 shows one example of allocation of compression rate, horizontalblanking period and redundancy level relative to the contents in a fifthembodiment.

FIG. 48 shows one example of main compression coding information,auxiliary compression coding information and compressed image data, andtransmission timing of audio packet in a sixth embodiment.

FIG. 49 shows another example of main compression coding information,auxiliary compression coding information and compressed image data, andtransmission timing of audio packet in the sixth embodiment.

DESCRIPTION OF EMBODIMENTS

Known systems of transmitting image data to minimize the delay timeinclude an uncompressed image data transmission system, but it hasinvolved the problem of requiring a high-transmission path if sendinglarge-size image data is intended. To solve this problem a system oftransmitting image data in a compressed form is proposed, but it has itsown problem that, once an error arises on the transmission path,displayed images are disturbed in compressed block units, each includinga plurality of pixels. There has been another problem that the dataquantity that can be transmitted during a blanking period in which higherror-resistivity is ensured is smaller than that can be transmittedduring a valid pixel period.

In the following embodiments, solution of this problem is attempted byaccomplishing data compression in compressed block units in a system oftransmitting image data under compression to generate compression codinginformation and transmitting a more important part of the compressioncoding information out of the generated compression coding information(hereinafter to be referred to as main compression coding information)in a blanking period in which error-resistivity is higher. To add, otherparts of the compression coding information (hereinafter to be referredto as auxiliary compression coding information), like compressed imagedata, are transmitted during a valid period. These embodiments will bedescribed below with reference to drawings.

Embodiment 1

The modes of materializing image transmission devices and imagereceiving devices in these embodiments will be described below.

FIG. 1, a block diagram illustrating the image transmission system ofthis embodiment, shows a configuration connecting image transmittingdevice 100 and an image receiving device 200 by a cable 300.

The image transmitting device 100 is an image transmitting device, anequipment item that transmits image data, outputting to anotherequipment item over an HDMI cable or the like image data obtained byreceiving digital broadcasts, decoding them into a visible and audibleform, image data recorded on a recording medium or image dataphotographed with a camera or the like. Examples of the imagetransmitting device 100 include recorders, digital TV sets with abuilt-in recording function, personal computers with a built-in recorderfunction, and mobile telephones or camcorders mounted with a camerafunction and a recorder function.

The image receiving device 200 is a display device that uses an HDMIcable or the like to receive inputs of image data and outputs images ona monitor. Examples of the image receiving device 200 include digital TVsets, display sections, projectors, mobile telephones and signageequipment.

The cable 300 is a data transmission path for carrying out datacommunication, such as that of image data between the image transmittingdevice 100 and the image receiving device 200. Examples of the cable 300include a wire cable satisfying the HDMI standards or the DisplayPortstandards, and a data transmission path for wireless data communication.

First, the configuration of the image transmitting device 100 will bedescribed.

Input sections 101, 102 and 103 are input sections for inputting imagedata to the image transmitting device 100. One example of image datainputted to the input section 101 and processed by a tuner receptionprocessor 105 is a digital broadcast inputted as electric waves from arelay station of a broadcasting station, a broadcast satellite or thelike. To the input section 101, such electric waves from a relay stationof broadcasting station, a broadcast satellite or the like are inputted.

One example of image data inputted to the input section 102 andprocessed by a network reception processor 106 is a digital broadcast orinformation contents distributed via a network by using broadbandconnection of the Internet.

One example of image data inputted to the input section 103 andprocessed by a medium controller 107 is contents recorded on an externalrecording medium connected to the input section 103. Another example ofimage data processed by the medium controller 107 is contents recordedin a recording medium 108 built into the image transmitting device 100.Examples of the recording medium 108 include an optical disk, a magneticdisk and a semiconductor memory.

The tuner reception processor 105 is a reception processor that convertsan inputted electric wave into a bit stream, and it subjects theelectric wave of the RF (Radio Frequency) band to frequency conversionto the IF (Intermediate Frequency) band and demodulates the modulationapplied to the demodulated bit stream as signals of a certain band notdependent on the reception channel.

Examples of bit stream include an MPEG2 transport stream (hereinafterreferred to as MPEG2-TS) and a bit stream of a format complying withMPEG2-TS. Descriptions of bit stream in the following paragraphs willrefer to MPEG2-TS as a representative one.

The reception processor 105 further detects and corrects any code errorhaving arisen on the way of transmission and, after descrambling theMPEG2-TS, selects one transponder frequency at which programs forplaying back or recording are multiplexed, and separates a bit stream inthis selected one transponder into one program of audio and a videopacket.

The MPEG2-TS from the tuner reception processor 105 is supplied to astream controller 111 via a data bus 181. The stream controller 111, tokeep the intervals at the time packet reception by the tuner receptionprocessor 105, detects PTS (Presentation Time Stamp), which is a timemanagement information item, and an STC (System Time Clock) within areference decoder of the MPEG system, and adds a time stamp at a timingcorrected according to the result of detection.

The time stamp-augmented packet is supplied to either a decoder section112 or the recording medium controller 107 or to both. A data path 194to the decoder section 112 is used for processing when image data are tobe played back, and a data path 193 to the recording medium controller107 is used when recording image data onto a recording medium,

To a data path 192 of the stream controller 111, the MPEG2-TS comingfrom the input section 102 via the network reception processor 106 isinputted. The data path 192 is an input section that acquires a digitalbroadcast or digital contents distributed via a network.

Further, an external recording medium connected to the input section103, or a digital broadcast or digital contents recorded on therecording medium 108 built into the image transmitting device 100 isread out as the MPEG2-TS by the recording medium controller 107, andinputted to the stream controller 111 via the data path 193. The streamcontroller 111 selects at least one of these inputs, and outputs it orthem the decoder section 112.

The decoder section 112 decoded the MPEG2-TS inputted from the streamcontroller 111, and outputs the thereby generated image data to adisplay processor 113. The display processor 113, after subjecting theinputted image data to, for instance superposition of OSD (On ScreenDisplay), rotation, expansion or contraction, or frame rate conversion,outputs the processed data to a compression processor 114.

The compression processor 114 compresses the image data from the displayprocessor 113, and outputs the compressed data to a data transmissionsection 115.

The data transmission section 115 converts the image data compressed bythe compression processor 114 (hereinafter to be referred to ascompressed image data) into signals in a form suitable for transmission,and outputs it from an output section 116. Regarding the transmission ofthe image data, one example of signals in a form suitable fortransmission is described in the HDMI standards. In HDMI, a datatransmission format of the TMDS system is adopted for image data.

An input section 104 is an input section for inputting signals forcontrolling the operation of the image transmitting device 100. Examplesof the input section 104 include a receiver unit for signals transmittedfrom a remote controller and a button fitted onto a device body. Controlsignals from the input section 104 are supplied to a user IF 109. Theuser IF 109 outputs signals from the input section 104 to a controller110. The controller 110 controls the whole image transmitting device 100in accordance with signals from the input section 104. One example ofthe controller 110 is a microprocessor. The image data from the imagetransmitting device 100 is supplied to the image receiving device 200via the cable 300.

Next, the configuration of the image receiving device 200 will bedescribed.

Signals in a form suitable for cable transmission are inputted to aninput section 201. The signals inputted to the input section 201 aresupplied to a data reception processor 205.

The data reception processor 205 performs processing conversion ofsignals in a form suitable for cable transmission into prescribeddigital data, and outputs the converted digital data to an expansionprocessor 206.

The expansion processor 206 expands the compression processingaccomplished with the compression processor 114 in the imagetransmitting device 100 to generate image data, and outputs theprocessed data a display processor 207.

The display processor 207 subjects the inputted image data to displayprocessing. Examples of display processing include OSD superposition,expansion or contraction for conversion into the resolution of a displaysection 208, rotation and frame rate conversion. The output of thedisplay processor 207 is supplied to the display section 208.

The display section 208 converts the inputted image data into signalsmatching the display system and displays the converted signals on ascreen. Examples of the display section 208 include a liquid crystaldisplay, a plasma display, an organic EL (Electro-Luminescence) displayand a projector-projected display.

An input section 202 is an input section for inputting signals forcontrolling the operation of the image receiving device 200. Examples ofthe input section 202 a receiver unit for signals transmitted from aremote controller and a button fitted onto a device body. Controlsignals from the input section 202 are supplied to a user IF 203. Theuser IF 203 outputs signals from the input section 202 to a controller204. The controller 204 is a controller that controls the whole imagetransmitting device 200 in accordance with signals from the inputsection 202.

FIG. 2 shows a valid period in which image data of one frame period aretransmitted and a blanking period in which no image data aretransmitted.

The area denoted by 400 represents a vertical period, and the verticalperiod 400 includes a vertical blanking period 401 and a vertical validperiod 402. A VSYNC signal is a one-bit signal, 1 representing a periodof the prescribed number of lines from the beginning of the verticalblanking period 401 and 0 representing a period between any othervertical blanking period and a vertical valid period 402. One example ofprescribed number of lines is four lines.

The area denoted by 403 represents a horizontal period, and thehorizontal period 403 includes a horizontal blanking period 404 and ahorizontal valid period 405. An HSYNC signal is a one-bit signal, 1representing a period of the prescribed number of signal is a one-bitsignal, 1 representing a period of the prescribed number of from thebeginning of the horizontal blanking period 404 and 0 representing aperiod between any other horizontal blanking period and a horizontalvalid period 405. One example of prescribed number of pixels is 40pixels.

A valid period 406 is the area surrounded by the vertical valid period402 and the horizontal valid period 405 and image data are allocated tothis period. Further, a blanking period 407 is the area surrounded bythe vertical blanking period 401 and the horizontal blanking period 404.

In this embodiment in this configuration, compressed image data andauxiliary compression coding information are transmitted in the validperiod 406 and main compression coding information are transmitted inthe blanking period 407.

In the blanking period 407, audio data and other incidental data aretransmitted in a packetized form.

A method of reliably transmitting this packet containing audio data andthe like in the blanking period 407 is disclosed, in for instance, theJapanese Unexamined Patent Application Publication (Translation of PCTApplication) No. 2005-514873.

As error correction codes are included in packeted data in the blankingperiod in this configuration, errors arising on the transmission pathcan be corrected, resulting in strengthened error resistance. Further,as the configuration is such that the data to be transmitted in thepacketed form during the blanking period is transmitted over twophysically different channels, and the transmission channel is switchedover at prescribed intervals of time, an error having arisen on onechannel in a burst mode does not affect the pother channel, data errorscan be corrected. The correction rate of errors is sufficient to achievean improving effect of 10⁻¹⁴ in the horizontal blanking period against10⁻⁹ in horizontal valid period.

In this example, 24 bits of image data per clock are transmitted duringthe valid period 406, and in the blanking period 407 one packetincluding a 3-byte header and 28-byte data is transmitted in a 32-clockperiod.

For instance, when 12 bits each of signals of horizontal 3840 validpixels, vertical 2160 valid lines and YCbCr luminance chromaticdifference are to be transmitted in the 444 format at a frame frequencyof 60 Hz, a very high clock frequency of 891 MHz is required. A highclock frequency not only needs a costly transmission and reception unitsbut also entails a decrease in cable length permitting stabletransmission of images, resulting in inconvenience in use.

This embodiment makes it possible to approach a practically useful clockfrequency, 594 MHz by ⅔ compression or 297 MHz by ⅓ compression. Furtherby the 444 format of 8 bits each the 422 format of 12 bits each of YCbCrluminance chromatic difference signals, a practically useful clockfrequency of 297 MHz can be achieved by ½ compression.

Where there are 3840 horizontal valid pixels and 2160 vertical validlines, for instance, the horizontal blanking period has 560 horizontalblanking pixels and the vertical blanking period has 90 verticalblanking lines. The following description will refer to a case ofcompressing 12 bits each of YCbCr luminance chromatic difference imagesignals in the 444 format of 3840 horizontal valid pixels, 2160 verticalvalid lines and 60 Hz frame frequency are compressed to ⅓ by way ofexample.

The clock frequency after compression is 297 MHz and, in a transmissionunder the conditions of 1940 horizontal valid pixels, vertical 2160valid lines, 280 horizontal blanking pixels and 90 vertical blankinglines, permits easy reproduction of the original clock of 594 MHz,double the transmission frequency, on the receiving side on a stablebasis. During the period of horizontal valid pixels if 12 bits of YCbCrluminance chromatic difference signals per pixel, or a total of 36 bitsare compressed to ⅓, namely 12 bits, 24 bits per pixel after thecompression can be transmitted, and therefore two pixel-equivalent ofthe original pixel can be transmitted, resulting in halving of theoriginal clock frequency after the compression.

Since one packet per 32 clocks can be transmitted, a maximum of eightpackets of 280 compressed horizontal blanking pixels can be transmitted.On the other hand, 24 bits×8 ch of audio data per packet can betransmitted. As the horizontal frequency of image data is 135 kHz (=60Hz×(2160+90)), when 24 bits of linear PCM audio data of 192 kHz samplesare to be transmitted over 8 ch, a maximum of two packets is required inone horizontal blanking period. It is desirable that, for the remainingsix packets, compression coding type information can be stated within168 bytes (=28 bytes×6 packets).

On the other hand, when the aforementioned 32 pixels are to becompressed as a unit block, a stating space for YCbCr luminancechromatic difference signals equivalent to 120 blocks of information ofdifferent compression coding systems, or an equivalent of 360 blocks intotal, is needed because there are 3840 horizontal valid pixels. If themain compression coding information is expressed in three bits forinstance, the stating space will be equivalent 135 bytes, permittingtransmissions of five packets, and it can be compatible with a largecapacity audio data transmission of 192 kHz, 8 ch.

FIG. 3 and FIG. 4 show examples of image data inputted to thecompression processor 114. Luminance signals of n pixels in thehorizontal direction and m lines in the vertical direction are shown.Chromatic difference signals, in the case of the 444 format, take on thesame format as luminance signals. Examples of the number of pixels n andthe number of lines m include a so-called full HD image of n=1920,m=1080, and a so-called 4k2k image of n=3840, m=2160.

Here, the unit block of image data compressed by the compressionprocessor 114 (hereinafter to be referred to as compressed block) shallbe 1 pixels in the horizontal direction and k pixels in the verticaldirection. In FIGS. 3, 501 and 502 represent cases of 1=32, k=1, and areconfigured of 32 consecutive pixels on the same line. In this image dataunit, the compression processor 114 carries out compression.

In FIGS. 4, 503 and 504 represent cases of 1=16, k=2, and are configuredof 16 consecutive pixels on two lines, upper and lower. In this imagedata unit, the compression processor 114 carries out compression. Forcompression processing, the configuration may as well have a horizontalcompressor and a vertical compressor, k1 and k2 (k1<k2) image data unitblocks made available, differing in the pixel number k in the verticaldirection, and the horizontal compressor and the vertical compressor 134respectively compressing the k1 image data unit blocks and the k2 imagedata unit blocks.

Although a case of 32 pixels has been described as an example of imagedata unit to be compressed, the unit may as well be 64 pixels or 128pixels.

When the inputted chromatic difference signals are in the 422 format,the data will have one pixel each of the Cb component and the Crcomponent of the chromatic difference signals alternately. For instancein a 4k2k image, they may as well be treated as image data of n=3840,m=2160 in the total of Cb components and Cr components. Since thecorrelation level is high among Cb components and among Cr components,the efficiency of compression can be enhanced by separating Cbcomponents and Cr components from each other, treating either ascomponents of n=1920, m=2160 and making them an image data unit block ofonly the same components to be compressed.

When the inputted chromatic difference signals are in the 420 format,the data will have one pixel each of the Cb component and the Crcomponent of the chromatic difference signals for four pixels of Ysignals. For instance in a 4k2k image, they may as well be treated asimage data of n=1920, m=2160 in the total of Cb components and Crcomponents. Since the correlation level is high among Cb components andamong Cr components, the efficiency of compression can be enhanced byseparating Cb components and Cr components from each other, treatingeither as components of n=1920, m=2160 and making them an image dataunit block of only the same components to be compressed.

The compression coding information is configured of main compressioncoding information and auxiliary compression coding information. On thebasis of the main compression coding information and the auxiliarycompression coding information, expansion of compressed image data tothe original image data can be processed.

With only main compression coding information, simple expansion orpartial expansion can be processed.

Main compression coding information is transmitted over a transmissionpath higher in error-resistivity than that for auxiliary compressioncoding information. In this embodiment, compressed image data andauxiliary compression coding information are transmitted to the validperiod 406, and main compression coding information is transmitted tothe blanking period 407. As an example of transmitting main compressioncoding information in the blanking period 407, there is a method bywhich common main compression coding information is transmitted in thevertical blanking period 401 line by line, main compression codinginformation on compressed blocks on the same line is transmitted in thehorizontal blanking period 404.

Where this configuration is used, even if an error occurs in auxiliarycompression coding information on a transmission path of a hightransmission error rate, the probability of error occurrence in maincompression coding information is significantly reduced. As a result,when an error has occurred in auxiliary compression coding informationon a transmission path of a high transmission error rate, disturbance ofdisplay can be restrained by using simply expanded or partially expandedimage data, created by utilizing main compression coding information,for error correction. Also, by including the compressed block size inmain compression coding information when an error has occurred inauxiliary compression coding information, disturbance of display can berestrained within the compressed block.

Further, compression coding information may as well be configured solelyof main compression coding information or auxiliary compression codinginformation.

An example of configuration of compression coding information andcompressed image data is shown in FIG. 5.

In this example, the unit of a compressed block 600 is configured ofsub-compressed blocks 610 and 620, and the sub-compressed block blocks610 and 620 are configured of pixels 611, 612, 613 and 614 and pixels621, 622, 623 and 624, respectively.

One example of configuration of a compressed block after compression isrepresented by 630. The compressed block 630 is configured ofcompression coding information 631 and compressed image data 632. Thecompressed image data 632 is a compressed image data set generated bycompressing pixel data sets 611, 612, 613, 614, 621, 622, 623 and 624.The compression coding information 631 is information generated bycompression processing. When compression coding information istransmitted in the valid period 406 in this configuration, if thetransmission error rate is high, the probability of error occurrencealso in the compression coding information increases, entailing aproblem that display disturbance becomes more likely to arise incompressed block units. Further, when compression coding information istransmitted in the blanking period 407, the quantity of transmittabledata becomes significantly smaller than in the valid period 406,entailing a problem of reduction in the quantity of compression codinginformation.

Another example of configuration of a compressed block after compressionis represented by 640. In this example, compression coding informationis configured of main compression coding information 641 and two kindsof auxiliary compression coding information 642 and 644. The compressedblock 640 is configured of the main compression coding information 641,the auxiliary compression coding information sets 642 and 644, andcompressed image data sets 643 and 645. The compressed image data 643 isa compressed image data set generated by compressing the image data sets611, 612, 613 and 614 belonging to the sub-compressed block 610. Theauxiliary compression coding information 642 is an information setgenerated by processing compression of the pixel data sets 611, 612, 613and 614. The compressed image data set 645 is a compressed image dataset generated by compressing the image data sets 621, 622, 623 and 624belonging to the sub-compressed block 620. The auxiliary compressioncoding information 644 is an information set generated by processingcompression of the pixel data sets 621, 622, 623 and 624.

Another example of configuration of a compressed block after compressionis represented by 650. In this example, compression coding informationis configured of two kinds of information including main compressioncoding information 651 and auxiliary compression coding information 652.The compressed block 650 is configured of the main compression codinginformation 651, the auxiliary compression coding information 652 andcompressed image data 653. The compressed image data 653 is a compressedimage data set generated by compressing the image data sets 611, 612,613, 614, 621, 622, 623 and 624 contained in the compressed block 600.The main compression coding information 651 and the auxiliarycompression coding information 652 are information sets generated byprocessing compression of the compressed block 600.

Another example of configuration of a compressed block after compressionis represented by 660. The difference between this example and thecompressed block 650 after compression lies in that auxiliarycompression coding information 662 is information generated by furthercompressing the auxiliary compression coding information 652 in thecompressed block 650 after compression. Though not illustrated here, thequantity of transmitted data may be reduced by further compressing themain compression coding information 651.

Where the aforementioned configuration of the compressed blocks 640, 650and 660 after compression is adopted, it becomes possible to restrainthe influence of any transmission error on the displayed image (restoredimage) while suppressing the quantity of data transmitted over the moreerror-resistive transmission path by transmitting main compressioncoding information over a more error-resistive transmission path thanauxiliary compression coding information.

FIG. 6 illustrates the transmission timing for the compressed blocks640, 650 and 660 after compression shown in FIG. 5. Reference numerals700 and 702 denote the valid period 406, and 701 denotes the horizontalblanking period 404. Reference numerals 710, 711 and 712 denote oneline-equivalent of image data before compression to be transmitted inthe valid period 700. In this example, the three compressed blocks 710,711 and 712 are processed for compression.

Reference numeral 730 denotes main compression coding informationgenerated by processing compression of the compressed blocks 710, 711and 712. Reference numerals 731, 732 and 733 denote compressed blocksgenerated by processing compression of the compressed blocks 710, 711and 712. The compressed blocks are configured of compressed image dataand auxiliary compression coding information generated by compressionprocessing. As one example of the configuration of the compressed block731, 740, 750 and 760 are shown. They respectively correspond to thesub-compressed blocks 640, 650 and 660 after compression shown in FIG.5.

The main compression coding information 730 is transmitted in thehorizontal blanking period 701, which is more error-resistive than thevalid periods 700 and 702. Further, the compressed blocks 731, 732 and733 after compression configured of compressed image data generated byprocessing compression of the image data 710 and auxiliary compressioncoding information are transmitted over the valid period 702, next tothe horizontal blanking period 701. To add, some or all of maincompression coding information may as well be transmitted in thevertical blanking period 401.

One example of main compression coding information and auxiliarycompression coding information will be described with reference to FIG.28.

Here is considered a case of compression processing in which the unit ofcompressed blocks 920 is 32 horizontal pixels and that of sub-compressedblocks 921, 922, 923 and 924 is 8 pixels. Compression coding information926 for the leading sub-compressed block 921 is supposed to be maincompression coding information, and compression coding information sets927, 928 and 929 for the other three sub-compressed blocks are supposedto be auxiliary compression coding information.

The main compression coding information is configured of the compressioncoding information 926 for the leading sub-compressed block 921 andother compression coding information sets for use in the processing toexpand the sub-compressed block 921 (for instance the common compressioncoding information 925 for the sub-compressed blocks and the like).

The auxiliary compression coding information is configured of thecompression coding information sets 927, 928 and 929 for the second andsubsequent sub-compressed blocks 922, 923 and 924.

The use of the configuration of this example enables display disturbanceto be restrained by using, when an error has occurred in the auxiliarycompression coding information on a transmission path of a hightransmission error rate, image data belonging to the leadingsub-compressed block expanded by the use of the main compression codinginformation for correction of the error. One example of such errorcorrection is generating and displaying a complementing image belongingto the error-ridden sub-compressed block from image data belong to theleading sub-compressed block out of the compressed blocks expanded bythe use of the main compression coding information.

One example pertinent to the transmission path is a method by whichauxiliary compression coding information (FIG. 28(c)) and a compressoroutput (FIG. 28(d)) are transmitted in the valid period 406 and maincompression coding information is transmitted in the horizontal blankingperiod 404 greater in error-resistivity.

Another example of main compression coding information and auxiliarycompression coding information will be described with reference to FIG.27.

Here is considered a case of compression processing in which the unit ofcompressed blocks 900 is 32 horizontal pixels and that of sub-compressedblocks 901, 902, 903 and 904 is 8 pixels.

A first compressor (compressor A133) processes first compression of thesub-compressed blocks 901, 902, 903 and 904 in sub-compressed blockunits, and auxiliary compression coding information sets (firstcompression coding information sets 905, 906, 907 and 908) insub-compressed block units and compressed image data sets (firstcompressed image data sets 909, 910, 911 and 912). A second compressor(compressor B134) further processes second compression of four inputtedcompressed image data sets (first compressed image data 909, 910, 911and 912) in sub-compressed block units, and generates one each of maincompression coding information set (second compression codinginformation set 914), compressed image data set (second compressed imagedata set 914) and compressed image data set (second compressed imagedata set 915). By transmitting the main compression coding informationover a transmission path higher in error resistivity than thetransmission path for the auxiliary compression coding information sets(first compression coding information sets 905, 906, 907 and 908) andthe compressed image data set (second compressed image data set 915),expansion can be processed even in sub-compressed block units on thetransmission path higher in transmission error rate, and the rangeaffected by errors can be restrained to the range of sub-compressedblocks.

Error resistivity can be further enhanced by transmitting a commoncompression coding information set 913 for the first compression codinginformation sets 905, 906, 907 and 908 as main compression codinginformation in addition to the second compression coding information914.

As another instance of compression coding information, here isconsidered compression processing in which, for instance, the compressedblock unit is 32 horizontal pixels and the sub-compressed block unit is8 pixels, and size information is added in sub-compressed block units.The overall total of size information sets in sub-compressed block unit,namely size information on compressed block unit is included in maincompression coding information, and size information is included inauxiliary compression coding information in sub-compressed block unit.By transmitting the main compression coding information over atransmission path higher in error resistivity, if an error arises in theauxiliary compression coding information on a transmission path higherin transmission error rate, the error can be prevented from affectingthe next compressed block by generating the size of compressed blockunits on the basis of the main image coding information and skippingexpansion processing equivalently to that size.

If there is a surplus capacity for data transmission on a transmissionpath higher in error resistivity, the whole size information onindividual sub-compressed blocks may as well be transmitted as maincompression coding information. In this case, if an error arises inauxiliary compression coding information, the error can be preventedfrom affecting other sub-compressed blocks by generating the size of thesub-compressed block in which the error has occurred on the basis of themain image coding information and refraining from expansion processingequivalently to that size.

FIG. 7 is a block diagram showing one example of the compressionprocessor 114.

An input section 130 is an input section for inputting image data to thecompression processor 114.

The inputted image data are supplied to a compressor A133, a compressorB134 and a compressor C135. The compressor A133, compressor B134 andcompressor C135 process compression of the inputted image data indifferent ways from one another, and generate compression codinginformation and compressed image data. To add, any other compressor thanwhat is designated by a control signal 131 can be suspended fromcompression processing or the action clock itself can be stopped to savepower consumption.

Each of the compressor A133, compressor B134 and compressor C135 isconfigured of a compressing circuit that compresses a plurality of imagedata sets constituting a compressed block. One example of compressionformula can be configured by operating Wavelet conversion in thehorizontal direction and coding the result of the arithmetic operation.As the compression formula, Hadamard transform, run length encoding,Huffman encoding, differential encoding or the like may be applied.

Further, as another example of compression formula, a compressingcircuit that compresses a plurality of image data sets in the verticaldirection. By one example of compression formula, first a difference istaken in the vertical direction for compressing a unit block of imagedata of two lines in the vertical direction and 16 pixels in thehorizontal direction, and then a difference is taken in the horizontaldirection. A compression formula of encoding the result can be used.

One example of other compression formulas uses a circuit that, whenchromatic difference signals of the 444 format or 422 format areinputted, curtails them into the 422 format or the 420 format. When the444 format or the 422 format is inputted, if a prescribed compressionrate is surpassed in the compression processor 114 shown in FIG. 8 to bereferenced afterwards, curtailment to the 422 format or the 420 formatmay be processed as well.

The compression rate in this context means the ratio of the dataquantity after compression to that before compression. If, for instance,the data quantity before compression is 100 and the data quantity aftercompression is 30, the compression rate is 30%. Therefore, the higherthe compression rate, the greater the data quantity after compression,resulting in less deterioration of picture quality.

FIG. 10 is a block diagram showing one example of configuration of thecompressor A133.

An input section 150 is an input section for inputting image data to thecompressor A133.

An input section 151 is an input section for inputting control signalsfor controlling the compressor A133.

A first compressor 153 is a block that processes compression of inputtedimage data and generates compression coding information and compressedimage data. The compression coding information generated by the firstcompressor 153 is supplied to the compressed code information generator155. Further, the compressed image data generated by the firstcompressor 153 are supplied to a selector 156.

The compressed code information generator 155 is a block that generatesmain compression coding information and auxiliary compression codinginformation from the inputted compression coding information. Thecompressed code information generator 155 may as well have a memory fortemporarily storing the generated main compression coding informationand auxiliary compression coding information.

The selector 156 is a block that selects and outputs the compressedimage data supplied from the first compressor 153 and the maincompression coding information and auxiliary compression codinginformation data supplied from the compressed code information generator155.

FIG. 11 is a block diagram showing one example of configuration of thecompressor A133.

An input section 160 is an input section for inputting image data to thecompressor A133.

An input section 161 is an input section for inputting control signalsfor controlling the compressor A133.

A first compressor 163 is a block that processes first compression ofinputted image data and generates auxiliary compression codinginformation and compressed image data. The auxiliary compression codinginformation generated by the compressor 163 is supplied to a selector166. Further, the compressed image data generated by the firstcompressor 163 are supplied to a second compressor 164.

The second compressor 164 is a block that processes second compressionof inputted compressed image data and generates main compression codinginformation and compressed image data. The main compression codinginformation and compressed image data generated by the second compressor164 are supplied to a selector 166.

The selector 166 is a block that selects and outputs auxiliarycompression coding information supplied from the first compressor 163and main compression coding information and compressed image datasupplied from the second compressor 164.

The configuration of this example makes possible the processing ofcompression in two stages shown in FIG. 27. Further, though this exampleis a case of using two compressors, compressors may as well be providedfor three or more stages.

The outputs of the compressor A133, compressor B134 and compressor C135are supplied to a selector 136.

Although the description of this case refers to a compression processorhaving three compressors 133, 134 and 135, the number of compressors mayas well be only one or two, or four or more.

The selector 136 selects out of the compressor A133, compressor B134 andcompressor C135 what satisfies a compression rate requirement and has ahigh picture quality index, and supplies it to an error correction codegenerator 137. The picture quality index is an index whose valueimproves with a decrease in difference between, for instance, image datarestored from compressed image data and image data before compression.The highest level is achieved no compression loss arises and reversiblecoding is accomplished. To simplify the calculation of the picturequality index, the value of the picture quality index may be prepared inadvance for each different compression formula. It may be so definedthat a higher picture quality index is achieved when reversible codingis accomplished after curtailment to the 422 format than whencompression is done without changing from the 444 format to invitegeneration of compression loss. If compression rather results in anincreased data quantity, a prescribed compression rate is achieved byopting for curtailment to the 422 format or the 420 format beforecompression or reducing the number of quantified bits, and a picturequality index is so set as to match the curtailment or the reduction inthe number of quantized bits.

Also, the operation of any one of the compressor A133, compressor B134and compressor C135 may be validated with a control signal inputted froman input section 131, with the two others suspended from operation. Inthis case, control information indicating the compressor whose operationis valid is inputted to the selector 136 from the input section 131. Theselector 136, on the basis of the control information, outputs an outputsignal of the compressor whose operation is valid to the errorcorrection code generator 137.

An error correction code generator 136 calculates an error correctioncode for each unit of image data compressed by the compressor C135,compressor A133 and compressor B134 (compressed image data), adds thecode to the compressed image data, and outputs the image data units to amemory controller 139. Available systems of error correction include theCRC (Cyclic Redundancy Check) system and the parity check system.

Whether or not to add the error correction code may be determinedaccording to the data transmission capacity. The reason is that, if thedata transmission capacity of the cable is limited, adding the errorcorrection code would involve curtailment of more pixels or tones ofgradation and accordingly invite picture quality deterioration over thewhole screen. If there is a surplus in transmission capacity, the errorcorrection code may be added to the compressed image data to enhanceerror resistivity. Determination of whether or not to process errorcorrection may be left to the receiving side by transmitting togethermetadata on whether or not error correction is added to compressed imagedata. Also, the error resistivity level may be varied by altering errorcorrection processing according to the compression formula applied, orinformation indicating what error correction code has been added may aswell be added as metadata. Or no error correction may be processed andinput data may be outputted as they are.

The memory controller 139 temporarily accumulates in a memory unit 140compressed image data, main compression coding information and auxiliarycompression coding information supplied from an error code generator137. It also reads the main compression coding information and thecompressed image data out of the memory unit 140 and outputs them in thevalid period 406. Further, it reads the main compression codinginformation out of the memory unit 140, and outputs it in the horizontalblanking period 404 immediately preceding the valid period 406 in whichthe compressed image data are outputted. By another formula, any ofcompressed image data, main compression coding information and auxiliarycompression coding information with an error correction code for oneline may be transmitted in the valid period 406 for one line thereby toincrease the transmission quantity. Also, the reliability of errorcorrection may be enhanced by containing the error correction code inthe main compression coding information and outputting the informationin the horizontal blanking period 404.

An output section 132 outputs compressed image data, main compressioncoding information and auxiliary compression coding information from thememory controller 139. Though not shown, operations of the blocks inFIG. 7 are controlled in accordance with control signals from thecontroller 110 shown in FIG. 1.

FIG. 12 is a block diagram showing one example of configuration of theerror correction code generator 136. To the input section 170,compressed image data is inputted. The compressed image data is inputtedto a holding unit 175 and an error correction code calculator 173. Theerror correction code calculator 173 subjects the inputted compressedimage data to a cyclic operation using a generating polynomial.

Examples of Generating Polynomial Include:G(X)=X ¹⁶ ×X ¹² ×X ⁵+1  (Mathematical expression 1)This generating polynomial gives a cyclic operation taking an exclusiveOR of the bits in the inputted compressed image data. The unit of theoperation shall be the unit of the compressed image data.

An input section 171, to which a signal indicating the period duringwhich compressed image data is entered is inputted, supplies this signalto a timing generator 174. The timing generator 174 outputs a signalindicating that a unit block equivalent of image data to count andcompress the valid period of the compressed image data has beenprocessed to the data holding unit 175 as an error correctioncalculation result output timing signal. Further, the timing generator174 outputs together to the data holding unit 175 a timing signalindicating the input period of compressed image data and a timing signalindicating the compressed image data and the results of calculating theerror correction code.

The data holding unit 175 temporarily stores, in accordance with thetiming indicated by the timing generator 174, the results of calculationby the error correction code calculator 173 and the compressed imagedata into, for instance, a memory, flip-flop, delay element or the like,and successively outputs them to the output section 132.

FIG. 13 is a block diagram showing one example of configuration of thedata transmission section 115.

An input section 180 outputs compressed image data to a serializer 184.Further, an input section 181, to which the clock of image data isinputted, outputs it to a PLL 186 and an output section 182.

As the clock of image data, a clock synchronized with the pixel clockused in the standard timing format of uncompressed image data is used.For instance, a clock obtained by half division of the pixel clock ofuncompressed image data is used. In this case, as the clock will be ½and the number of quantized bits will be 8/12 if the uncompressed imagedata are 12-bit quantized image data, the aforementioned prescribedcompression rate should be set ⅓ or less. The clock may be ¾ multipliedor ⅔ multiplied instead of being half divided. Using the clocksynchronized with the pixel clock of uncompressed image data fortransmitting the compressed image data provides the advantage that thereceiving side, when restoring the uncompressed image data, can minimizethe jittering of restored data by using a clock resulting from 4/2, 4/3or 3/2 multiplication of the transmission clock as the pixel clock.

The PLL 186 generates a clock or clocks by multiplying or dividing theinputted clock. Examples of multiplication include fivefold or tenfoldmultiplication of the frequency of the inputted clock. Either only onetype of clock or two types of clock may be chosen for the clockgenerated by the PLL 186. One example of one type of clock is atenfold-multiplied product of the inputted clock. Examples two types ofclock included a first clock speed giving priority to the datatransmission quantity and a second clock speed slower than the firstclock speed to give priority to reducing the frequency of erroroccurrence. Examples of speed include the first clock speed oftenfold-multiplied product of the input clock and the second clock speedof fivefold-multiplied product of the input clock.

The multiplied clock or clocks generated by the PLL 186 are outputted tothe serializer 184.

The serializer 184 serializes the compressed image data of the inputtedYCbCr luminance chromatic difference signals bit by bit with atenfold-multiplied clock, and outputs the serialized data to a levelconverter 185. When there are 8 bits of data to be inputted to the inputsection 180 per clock inputted to the input section 181, the TMDStransmission method, for instance, may be used by which DC components ofa bit stream resulting from mapping and serializing the eight-bit dataare suppressed. Where there are three cables to be connected to anoutput section 176, 24 bits of compressed image data per input clock canbe transmitted by serializing the data for each individual cable.

The level converter 185 outputs signals of a form suitable for cabletransmission via the output section 182.

FIG. 8 is a block diagram showing another example of configuration ofthe compression processor 114.

A memory controller 142 temporarily accumulates in the memory unit 140compressed image data, main compression coding information and auxiliarycompression coding information supplied from the error code generator137. It also reads auxiliary compression coding information andcompressed image data out of the memory unit 140, and outputs them inthe valid period 406. It further reads main compression codinginformation out of the memory unit 140, and outputs it in the horizontalblanking period 404 immediately preceding the valid period 406 in whichcompressed image data are outputted. Further, it can read compressedimage data out of the memory unit 140 and supply them to a selector 141.

The selector 141 is a block that selects either image data inputted fromthe input section 130 or compressed image data 143 supplied from thememory controller 142 and supplies what it has selected to thecompressor A133, compressor B134 and compressor C135. It may as welloutput the image data inputted from the input section 130 to aprescribed compressor and at the same time output the compressed imagedata 143 to some other compressor. The configuration of this examplemakes possible two-stage compression processing shown in FIG. 27.Compression in three or more stages may also be processed.

FIG. 9 is a block diagram showing still another example of configurationof the compression processor 114.

A selector 138 outputs to a memory controller 145 main compressioncoding information and auxiliary compression coding information suppliedfrom the error code generator 137, and outputs to a selector 144compressed image data supplied from the error code generator 137.

The memory controller 145 temporarily accumulates in the memory unit 140main compression coding information and auxiliary compression codinginformation supplied from the selector 138. It also reads auxiliarycompression coding information out of the memory unit 140, and outputsit in the valid period 406, to be described afterwards, via the selector144. It further reads main compression coding information out of thememory unit 140, and outputs it via the selector 144 in the horizontalblanking period 404 immediately preceding the valid period 406 in whichit outputs auxiliary compression coding information.

The selector 144 is a block that selects compressed image data suppliedfrom the selector 138 and main compression coding information andauxiliary compression coding information data supplied from the memorycontroller 145, and outputs them to the output section 132.

In this example, the selector 138 may output auxiliary compressioncoding information, together with compressed image data, directly to theselector 144 without going via the memory controller 145. In this case,the memory controller 145 processes reading and writing of maincompression coding information out of and into a memory. By choosing theconfiguration of this example, the memory capacity of the memory unit140 on the transmitter 100 side can be kept small.

FIG. 14 through FIG. 17 show an example of packet for transmitting someof main compression coding information.

FIG. 14 and FIG. 16 show an example of packet header, which a commonheader type 0Bh, indicating that this is information regarding thecompression coding formula according to the invention, is stated in thefirst header block HB0. Each bit of HB1 and bits 4 through 7 of HB2 are0 for future expansion. Eco_Packet # shown in bits 0 through 3 of HB2indicates identification in the frame. FIG. 15 and FIG. 17 show anexample of data of 28 bytes transmitted following the header.

In the header of FIG. 14, 0h is allocated as Eco_Packet #, indicatingthat a packet configured of the header FIG. 14 and the data of FIG. 15is common information (main compression coding information) among theframes. This packet is arranged in a vertical blanking period, andtransmitted at least once for each image frame. The contents of the dataof FIG. 15 will be described below.

Color_Sample denotes color sample information; for instance, 0 is aYCbCr luminance chromatic difference signal in the 444 format(hereinafter referred to as YCbCr444), 1, a YCbCr luminance chromaticdifference signals in the 422 format (hereinafter referred to asYCbCr422), 2, a YCbCr luminance chromatic difference signals in the 420format (hereinafter referred to as YCbCr420), 3, an RGB signal in the444 format (hereinafter referred to as RGB444), and 4 through 7 forfuture expansion. To signals in the 422 format or the 420 format a bitindicating CbCr sample position information may as well be additionallyallocated.

Eco_Mem is 0 when a packet transmitting some of main compression codinginformation shown in FIG. 16 and FIG. 17 is to be described afterwardsto be transmitted in the horizontal blanking period immediatelypreceding the valid period 406 in which compressed image data istransmitted, and 1 when it is to be transmitted in the horizontalblanking period immediately following the valid period 406 in whichcompressed image data is transmitted.

CD denotes Color Depth; for instance, 4h is a 24-bit Color, a total of 8bits of YCbCr components, 5h, a 30-bit Color, a total of 10 bits ofYCbCr components, 6h, a 36-bit Color, a total of 12 bits of YCbCrcomponents, 7h, a 48-bit Color, a total of 16 bits of YCbCr components,and the rest for future expansion. This definition conforms to theHDMI-prescribed Deep Color Mode definition.

Eco_FLM is supposed to be 1 when the compression coding formulas of allblocks in the frame are the same, and 0 when the formula is to be setblock by block. Where it is 1, the compression coding formulas of Y, Cband Cr are respectively stated in Eco-CD0, Eco-CD1 and Eco-CD2 to bedescribed afterwards.

The ratio between CK_N and CK_M (CK_N/CMM) represents the frequencyratio between the pixel clock of uncompressed image data and the clockof the communication path for transmitting compressed data, for instancethe TMDS clock. For instance, if CK_M=2 when CMN=1, the TMDS clock ofthe transmission system is 297 MHz, ½ of 594 MHz of the pixel clock ofuncompressed image data at 4k2k.

Eco_Block denotes the number of pixels constituting a compressed block.

Eco_CD0 through Eco_CD3 denote four kinds of candidates for compressioncoding information to be applied to individual image data unit blocks.As in one example shown in FIG. 18, the four kinds are selected fromcompression coding information Eco_Code for units of image data to becompressed.

One or more of packets, each including a header shown in FIG. 16 anddata shown in FIG. 17, are transmitted in each horizontal blankingperiod. Eco_Packet # in the header shown in FIG. 16 denotes the serialnumber of the packet to be transmitted over each line, beginning with 1and successively increased by 1 each time.

Eco_length_0 through Eco_length_39 represent size information oncompressed blocks transmitted in the valid period 406. Examples of sizeinformation include the bit size and byte size of compressed blocks. Itmay as well be information on which the bit size and byte size ofcompressed blocks are based. For instance, there is a method by which,when a compressed block size S_Block takes on any value from 32 bits to64 bits at two-bit intervals, the bit size of a compressed block isdefined by the following equation.S_Block=32+(2×Eco_length_#)(# is 0 to 39)  (Mathematical expression 2)In the example above, Eco_length # is four bits.

Eco_length_# may be defined individually for each of Y, Cb and Cr, or bya value which is the total compressed block size of Y, Cb and Cr. In thelatter, the transmission quantity of Eco_length_# can be reduced to ⅓.

The compression coding information defined in compressed block units istransmitted as auxiliary compression coding information, together withcompressed image data in the valid period 406. Types of the auxiliarycompression coding information include Eco_Error_0 through 39 and Code_0through Code_39.

Eco_Error_0 through Eco_Error_39 represent an error coding formula. Theerror coding formula is an error correction coding formula in the errorcorrection code generator 136 for calculation regarding data transmittedin the valid period 406. Examples of error correction coding formulainclude the CRC (Cyclic Redundancy Check) formula and the parity checkformula.

Code_0 through Code_39 state numbers selected from four types ofcompression coding information stated by Eco_CD0 through Eco_CD3 of FIG.15 in the order of Y, Cb and Cr components in each image data unitblock. For instance, if Code_0 representing the compression codinginformation on the Y component in the first image data unit block is 1,Eco_CD1 is indicated. If Eco_CD1 indicates 10, it means data obtained bycompressing the 444 format Y component of the original image data fromFIG. 18 by the differential coding formula.

When the two vertical lines shown in FIG. 4 are to constitute an imagedata unit block, Code_0 on the first line indicates compression codinginformation on the image data unit block 503, and Code_0 on the secondline indicates compression coding information on the image data unitblock 504.

When Color_Sample in FIG. 15 indicates the 444 format, Code_1 denotescompression coding information on Cb of a first image data unit block,Code_2 denotes compression coding information on Cr of the first imagedata unit, and Code_3 denotes compression coding information on Y of asecond image data unit block. When Color_Sample indicates the 420format, Code_1 denotes compression coding information on Y of the secondimage data unit block, Code_2 denotes compression coding information onCb (Cr on even-number lines) of the first and second image data units,and Code_3 denotes compression coding information on Y of a third imagedata unit block. When Color_Sample indicates the 422 format, Code_1denotes compression coding information on Cb of the first and secondimage data unit blocks, Code_2 denotes compression coding information onY of the second image data unit, and Code_3 denotes compression codinginformation on Cb of the first and second image data unit blocks.

Further, when Code_0 indicates 0, it denotes Eco_CD0, or when Eco_CD0indicates 6, it means that, as seen from FIG. 18, the 444 format Y, Cband Cr components 12-bit data of the original image are curtailed to 8bits of the 420 format. As Code_0 of only the Y component determines thetransmission forms of Cb and Cr in this case, information of Code_1indicating the Cb component and that of Code_2 indicating the Crcomponents are unnecessary, and 0 may be stated regarding them.

Now, though not shown in FIG. 1, the image receiving device 200 ismounted with a ROM storing EDID (Enhanced Extended DisplayIdentification Data) manifesting the performance features of the imagereceiving device 200. Information to make possible determination ofwhether or not the image receiving device 200 is responsive tocompression or expansion may be added into this ROM. This enables theimage transmitting device 100 to read out of the ROM storing EDID of theimage receiving device 200 information to determine whether or not it isresponsive to compression or expansion and, if it is a responsivedevice, to transmit compressed image data or, if it is not a responsivedevice, to transmit the image in the usual size not compressed, therebyto keep compatibility also with an image receiving device not responsiveto compression processing. Or if it is a device that reads outinformation to determine whether or not the device is responsive to anerror correction coding formula for transmitting compression codinginformation in the valid period 406 and, if it is a responsive device,to process error correction coding and compression coding informationor, if it is not a responsive device, to transmit the image in the usualsize not compressed, thereby to keep compatibility also with an imagereceiving device not responsive to compression processing. Or if it isnot a responsive device, resistivity to transmission errors may beenhanced by using the error correcting function of packets in theblanking period 407. Also, the user may be notified by indicating on thedisplay section 208 that the image receiving device is not responsive tocompression, the image is in the usual size and there is noresponsiveness error correction coding.

An example of statement of this EDID is shown in FIG. 19. FIG. 19 showsan example of expansion into what is known as an HDMI-VSDB area.

At Bit 2 of Byte 6, an Eco_transfer flag is provided, which showswhether or not the device is responsive to the compressed codingtransmission formula of this embodiment. As this area has been treatedas a reserved area, it is stated as 0 in non-responsive legacyequipment, and only responsive equipment can maintain backwardinterchangeability by being stated as 1. Where this Eco_transfer flag is1, statement of Byte 9 and Byte 10 is validated.

Block_64 and Block_128 are flags indicate that the respective sizes ofimage data unit blocks to be compressed are 64 pixels and 128 pixels.The image data unit block size of 32 pixels is defined as a requiredmode in responding to this compressed image data transmission, and itsstatement is intentionally dispensed with for the sake of saving theEDID stating space.

Eco-Codes 1 through 4 are flags indicating responsiveness to compressedcoding formulas including the Wavelet conversion, run length encoding,Huffman encoding and differential encoding, whose respective examplesare show in FIG. 18.

CLK_1, CLK¾ and CLK½ are flags indicating responsiveness to modes inwhich the frequency of the TMDS transmission clock to 1/1, ¾ and ½,respectively of the uncompressed image data clock.

Eco_Errors 1 through 4 are flags which take on 1 to indicateresponsiveness to respectively prescribed error coding formulas or 0 toindicate non-responsiveness.

Eco_Mem takes on 1 when the main compression coding information is to betransmitted in the horizontal blanking period immediately preceding thevalid period 406 in which compressed image data are to be transmitted,and takes on 2 when it is to be transmitted in the horizontal blankingperiod immediately following the valid period 406 in which compressedimage data is to be transmitted. Numeral 3 indicates that it isresponsive to both, and 0 indicates that it is responsive to neither.

Or where the image transmitting device 100 is to be used as mobileequipment, since it has to be battery-driven, power consumption of theimage transmitting device 100 becomes a factor to influence the lengthof time it can be continuously used. In this case, power consumption canbe reduced by compressing image data for transmission and therebyreducing the data transmission quantity. This effect makes possiblesetting of a long continuously usable period by adding, for instance, afunction such as a “power saving mode” as an operating mode of the imagetransmitting device 100 and uncompressed image data when power issupplied from outside or transmitting compressed image data when theequipment is battery-driven.

FIG. 20 is a block diagram showing one example of configuration of thedata reception processor 205.

An input section 220 outputs signals converted by a level converter 175of the image transmitting device 100 to a level converter 22.

The level converter 224 converts signals converted in level by the imagetransmitting device 100 into digital signals, and outputs them to adeserializer 225. One example of level conversion is conversion ofdifferential signals to single-end signals.

An input section 221 inputs a clock outputted from the imagetransmitting device 100 and outputs it to a PLL 226. The PLL 226generates a clock 10 times the inputted clock, and outputs it to thedeserializer 225. Further, the PLL 226 outputs from an output section222 the pixel clock to be used in the image receiving device 200. Whenthe pixel clock of uncompressed image data of the original image is usedin an image display device 200, a clock resulting from (CK_M/CK_N)multiplication of the input clock by the PLL 226 on the basis of packetdata in FIG. 13 is outputted from an output section 223.

The deserializer 225 parallelizes serialized data with a clock from thePLL 226 and outputs the parallelized data from the output section 222.The deserializer 225 parallelizes data of a tenfold clock, turns theminto eight-bit parallel data by prescribed TMDS decoding or the like,and outputs them from the output section 222.

FIG. 21 is a block diagram showing one example of configuration of theexpansion processor 206. Further, FIG. 26 is an explanatory drawing oftiming illustrating the processing concept of the expansion processor206 regarding the compressed block shown in FIG. 4. An input section 230is a data input section of the expansion processor 206. Data inputted tothe input section 230 includes HSYNC (FIG. 26 (a)) and VSYNC indicatingsync signals of image data, compressed image data and auxiliarycompression coding information sets 812 and 814 in the valid period 406,and main compression coding information sets 811 and 813 in thehorizontal blanking period 404. To an input section 231, the pixel clockof uncompressed image data after restoration, a compressed image dataclock and the like are inputted.

HSYNC, VSYNC, compressed image data clock and the pixel clock ofuncompressed image data after restoration are supplied to a timinggenerator 236. The timing generator 236 controls a counter with inputtedHSYNC and VSYNC, and generates and outputs timings needed for thecontrol of blocks in the expansion processor including timings for thevertical blanking period 401, the vertical valid period 402, thehorizontal blanking period 404, the horizontal valid period 405 and thevalid period 406.

A compression coding information extractor 233 extracts compressioncoding information on each image data unit block sent in horizontalblanking periods, and stores it into a compression coding informationmemory 234.

The period of this storage is shown in FIG. 26(c). Since the maincompression coding information set 811 is data matching the compressedimage data set 812 that follows, a period 815 of storing the informationuntil the second-line main compression coding information 813 arrives issufficient. However, where two lines of image data are verticallycompressed for instance, at least compression coding information 816 forvertical expansion has to be held until the period of expand thesecond-line compressed image data.

Compressed image data arriving within the horizontal valid periodundergo correction of errors in the transmission system by an errorcorrector 235. The error corrector 235 calculates for each unit ofcompressed image data the same error correction code as what the errorcorrection code generator 137 does. The result of this calculation andan error correction code inputted from the compression codinginformation extractor 233 are compared and, if the result of comparisonindicates any difference, error correction is processed. One example oferror correction processing is CRC operation. Or, only error detectionmay be done, leaving interpolation for errors to be done in subsequentprocessing.

The inputted compressed image data are supplied to an expander A237, anexpander B238 and an expander C239.

The expander A237, expander B238 and expander C239 processes expansionof the compressed image data each in a different way on the basis ofinformation in the compression coding information memory 234 to generateexpanded image data, and outputs them to a selector 261.

FIGS. 26(d) and 26(e) respectively show output data of each expanderwhen the compressed blocks shown in FIG. 4 are processed for horizontalexpansion by the expander A237 and processed for vertical expansion bythe expander B238. Horizontally expanded image data 818 and 819represent the output data of the expander A237, and the verticallyexpanded image data 820 and 821 represent the output data of theexpander B237.

The selector 261 appropriately selects, on the basis of information inthe compression coding information memory 234, image data to be inputtedto the input section 230, the output of the expander A237, the output ofthe expander B238 and the output of the expander C239, and outputs theselected data to an output section 232 as restored image data 824 (FIG.26(f)).

FIG. 25 is an explanatory drawing of timing illustrating the processingconcept of the expansion processor 206 when the compressed block shownin FIG. 3 is processed for horizontal expansion by the expander A237.

The input section 230 is a data input section of the expansion processor206. The data sets inputted to the input section 230 include HSYNC (FIG.26(a)) and VSYNC indicating sync signals of image data, compressed imagedata 802 and auxiliary compression coding information 804 in the validperiod 406, and main compression coding information sets 801 and 803 inthe horizontal blanking period 404. To the input section 231, the pixelclock of uncompressed image data, compressed image data clock and thelike after restoration are inputted.

The compression coding information extractor 233 extracts compressioncoding information on each image data unit block arriving in ahorizontal blanking period, and stores it into the compression codinginformation memory 234.

The period of that storage is shown in FIG. 25(c). Since the maincompression coding information 801 is a data set matching the compressedimage data 802 that follows, a storage period 805 for the informationuntil the arrival of the second line of the main compression codinginformation 803 will be long enough.

The inputted compressed image data is horizontally expanded by theexpander A237 to generate horizontally expanded image data sets 806 and807, which are expanded image data and outputted to the selector 261(FIG. 25(d)).

The selector 261 appropriately selects, on the basis of information inthe compression coding information memory 234, image data to be inputtedto the input section 230, the output of the expander A237, the output ofthe expander B238 and the output of the expander C239, and outputs theselected data to the output section 232 as restored image data sets 808and 809 (FIG. 25(f)).

FIG. 22 is a block diagram showing one example of configuration of theexpansion processor 206. This example is an expansion processor forwhich a formula of transmitting auxiliary compression coding informationis transmitted, together with compressed image data in the valid period406, instead of in the horizontal blanking period 404.

When the data to be transmitted in the valid period 406 is not onlycompressed image data but also includes compression coding information,some compression formula may require a reduction of the compression rateof the compressed image data, and in such a case the picture quality ofrestored images may deteriorate substantially. To prevent thisdeterioration, the horizontal blanking period is shortened to a lengthjust enough for transmission of two audio data transmission packets andthe horizontal valid period can be extended correspondingly. When 4k2kimage data of an uncompressed image is to be transmitted at a 297-MHzclock, half the 594 MHz of the pixel clock, it was 1920 for thehorizontal valid period and 280 for the horizontal blanking period inEmbodiment 1. For the transmission period of two audio packets,including guard bands before and after, 96 will be sufficient for thehorizontal blanking period, and according the horizontal valid periodcan be extended by the remaining 184. There is an effect of permittingextension of 1920 of the horizontal valid period by about 95%.

In this case, as the position and width of the horizontal sync signaldeviates from the standard timing of the prescribed uncompressed imagedata, it is advisable to so restore, with reference to uncompressedimage data SVDC (Short Video Descriptor) metadata assigned to the imagedata, the timing as to conform to the standard timing format on thereceiving side.

In FIG. 22, blocks having similar functions to their counterparts inFIG. 21 are assigned respectively the same reference numbers. Thedifference is the addition of a second image coding informationextractor 250 to the output section of an error correcting circuit 255.

In the example of FIG. 21, the compression coding information extractor233 extracts compression coding information (packets in FIG. 14 and FIG.15) in the vertical blanking period and compression coding information(packets in FIG. 16 and FIG. 17) in the horizontal blanking period. Inthis example, the compression coding information extractor 233 extractsonly the main compression coding information to be transmitted invertical blanking period or the horizontal blanking period, and storesit into the compression coding information memory 234.

In this example, instead of transmitting compression coding informationin a packet processed for error correction in the blanking period, errorcorrection similar to that for other compressed image data sets isprocessed. As a result, the main compression coding informationprocessed for error correction by the error corrector 255 and outputtedfrom the second compression coding information extractor 250 and theauxiliary compression coding information outputted from the compressioncoding information memory 234 are outputted to the expander A237, theexpander B238, the expander C239 and a selector 251.

In this example, since the compressed image data and the compressioncoding information are close to each other in timing, storage ofcompression coding information over one horizontal period is unnecessaryexcept for common compression coding information within the frame,resulting in an effect of permitting a reduction in circuit dimensions.

FIG. 23 is a block diagram showing another example of configuration ofthe expansion processor 206.

In FIG. 23, blocks having similar functions to their counterparts inFIG. 21 are assigned respectively the same reference numbers. Thedifference is the addition of a selector 260 at a stage preceding theexpanders.

The selector 261 appropriately selects, on the basis of information inthe compression coding information memory 234, image data inputted tothe input section 230 output, the output of the expander A237, theoutput of the expander B238 and the output of the expander C239, andoutputs the selected data to the output section 232. The selector 261can further select any of the output of the expander A237, the output ofthe expander B238 and the output of the expander C239, and output theselected one to the selector 260. By adopting the formula of thisconfiguration, extension by two or more formulas can be processed forcompressed image data inputted to the input section 230.

Though not shown, any of the output of the expander A237, the output ofthe expander B238 and the output of the expander C239 can be selected,and the selected one can be outputted to the compression codinginformation memory 234. The use of this configuration enables, forinstance, compressed auxiliary compression coding information 660 inFIG. 5 to be processed for expansion.

FIG. 24 is a block diagram showing still another example ofconfiguration of the expansion processor 206. In FIG. 24, blocks havingsimilar functions to their counterparts in FIG. 22 are assignedrespectively the same reference numbers. The difference is the additionof a memory 270 at the stage following the input section 230.

A selector 271 has a function to output selected data the memory 270 inaddition to the functions of the selector 251 shown in FIG. 22. Thememory 270 is a block that temporarily stores main compression codinginformation, auxiliary compression coding information and compressedimage data inputted from the input section 230 and expanded datasupplied from the selector 271, and supplies them to blocks of followingstages. By using this configuration, expansion of data inputted to theinput section 230 can be processed at a plurality of stages. If only onestage of expansion processing is needed, data supply from the selector271 to the memory 270 can be dispensed with.

The use of this configuration enables, for instance, expansion of imagedata compressed by the method shown in FIG. 8 or FIG. 11 to beprocessed.

Embodiment 2

Another mode of realizing the image transmission device and the imagereceiving device described as Embodiment 1 will be described below.

FIG. 29 shows one example of input and output waveforms of theserializer 184. The serializer 184 serializes compressed image datacorresponding to image data of inputted YCbCr luminance chromaticdifference signals (hereinafter referred to as YCbCr image data) orimage data of RGB signals (hereinafter referred to as RGB image data)with a tenfold multiplied clock into three one-bit data sets, and outputthem to the level converter 175.

In one example of serialization, image data of eight-bit YCbCr luminancechromatic difference signals or RGB signals is outputted in the order ofMSB or LSB from the beginning with a tenfold multiplied clock.

The level converter 185 outputs signals converted into a standard datatransmission format via the output section 182. Examples of standarddata transmission format include a differential level signal form of theTMDS formula. In a blanking period of images in this form, sincetransmission of no image data is needed, strength against transmissionerrors is increased in transmitting data other than image data by usingonly four-bit parts of the data of the tenfold multiplied clock to beserialized by the serializer 184 and not using the remaining six bits.Further, by using the two kinds of clocks, clocks generated by the PLL186 can be reduced to ½ of the clock for transmitting image data toobtain the same effect.

FIG. 30 shows one example of data composition of the serializer 184.There are three output lines of the serializer 184, of which one isconfigured of sync signals (HSYNC and VSYNC), a packet head and fixedbits. The configuration is such that the remaining two lines are usedfor transmitting data. The packet size is a 32-cycle equivalent of thetransmission clock.

FIG. 31 shows one example of data composition of audio data superposedin a horizontal blanking period. In the audio packet, sub-packets areconfigured generating seven-byte data with the same bits for two linesof data to be transmitted to the serializer and attaching an errorcorrecting code, such as a parity check, to the data. A packet for thehorizontal blanking period is configured in a format of four lines ofthe sub-packets and four bytes of a packet header.

As this configuration includes an error correcting code for sub-packetdata, an error occurring on the transmission path can be corrected toincrease error resistivity. Further, as data for transmitting sub-packetdata are configured in a zigzag form on two physically differentchannels, an error arising in a burst-like way does not affect the otherchannel, data error can be corrected. The error correction rate is highenough for an improving effect of 10⁻¹⁴ in the horizontal blankingperiod against 10⁻⁹ in the horizontal valid period.

It is advisable to transmit the error correction code of compressedimages as the highly error-resistive packet. The following descriptionwill take up as an example of number of transmittable packets a case inwhich the number of pixels in the horizontal period is 2200 and that ofpixels in the horizontal valid period is 1920. To add, the example ofimage form is YCbCr422.

Assuming the size of images to be compressed to be 64 pixels (32luminance pixels and 32 chromatic difference pixels), the size of 60error correction codes (2-byte) will require 120 bytes.

As the available capacity permits transmitting 28 bytes per packet, fivepackets will be a large enough size for the transmission. As thehorizontal blanking period has 280 pixels, eight packets can besuperposed. This configuration allows, even if a maximum of two packetsare provided for audio packets as 192 kHz 8ch LPCM audio transmitting,transmission of a maximum of five packets of the error correction codein the horizontal period.

When compressed image data of inputted RGB image data are to beoutputted to the data transmission section 115 in compressed block unitsover respectively prescribed TMDS channels, periods in which nocompressed image data are transmitted occurs between compressed blocks.Considered on a line-by-line basis, there is a problem that nosubstantial reduction of horizontal valid periods, compared with nocompression is done.

FIG. 32 shows one example of output waveforms on each of TMDS channel 0,TMDS channel 1 and TMDS channel 2 when compressed image data of inputtedRGB image data is to be outputted to the data transmission section 115.

The following description concerns a case in which compression isprocessed for each of R, G and B components of RGB image data in thisembodiment and R compressed image data, G compressed image data and Bcompressed image data are generated. CR0 and CR1 in the drawing arecompressed image data in sub-compression blocks, and a compressed blockis configured of CR0 and CR1. CR2 is the leading sub-block of the nextcompressed block. The same applies CG0, CG1, CG2, CB0, CB1 and CB2 aswhat applies to CR0, CR1 and CR2 mentioned above.

In this embodiment, it is made possible to reduce the non-transmissionperiod for compressed image data between compressed blocks andsub-compression blocks by transmitting R compressed image data clammedin bit units and transmitting them over TMDS channel 0.

FIG. 35 shows another example of output waveforms on each of TMDSchannel 0, TMDS channel 1 and TMDS channel 2 when compressed image dataof inputted RGB image data is to be outputted to the data transmissionsection 115.

In this embodiment, where sub-compression blocks 1300, 1301, 1302, 1305,1306, 1309 and 1310 cannot be divided into even numbers by 8 bits, theleading bit of any sub-compression block is caused to be positionedalways as the leading bit of a channel by adding stuffing data sets1303, 1304, 1307, 1308 and 1311 at the end. In this way, the receivingcircuit for sub-compression blocks on the image receiving device sidecan be simplified. Although stuffing data is added in sub-compressionblock units in this example, the addition may as well be done incompressed block units as shown in FIG. 36.

The examples of this embodiment described with reference to FIG. 32 andFIG. 35 involve a problem the transmission band occupied by transmittedcompressed image data is limited to the TMDS channel on which thecompressed data quantity is the greatest, entailing elongation of thevalid period, because compressed image data corresponding to RGB imagedata inputted to the data transmission section 115 is outputted torespectively prescribed TMDS channels.

FIG. 33 shows another example of output waveforms on each of TMDSchannel 0, TMDS channel 1 and TMDS channel 2 when R compressed imagedata, G compressed image data and B compressed image data, which arecomponents of compressed image data of inputted RGB image data, are tobe outputted to the data transmission section 115.

In this embodiment, R compressed image data, G compressed image data andB compressed image data are successively outputted in this order insub-compression block units to TMDS channel 0, TMDS channel 1 and TMDSchannel 2 successively in an interleaved way. Here is taken up, by wayof example, a case in which R compressed image data CR0 is in 18 bits, Gcompressed image data CG0 in 37 bits, B compressed image data CB0 in 8bits, R compressed image data CR1 in 20 bits, G compressed image dataCG1 in 18 bits and B compressed image data CB1 in 14 bits.

As the use of the above-described output formula enables compressedimage data corresponding to RGB image data inputted to the datatransmission section 115 to be transmitted over the three TMDS channelsin an evenly shared way, the valid periods for transmitting compressedimage data can be shortened. Although outputting in this case is done insub-compression block units in the order of RGB, it may as well be donein compressed block units as shown in FIG. 34.

FIG. 37 shows still another example of output waveforms on each of TMDSchannel 0, TMDS channel 1 and TMDS channel 2 when compressed image dataof YCbCr444 image data to be inputted to the data transmission section115 are to be outputted. The proportions of data quantities of thecomponents of YCbCr444 image data are the same among Y image data, Cbimage data and Cr image data. Incidentally, the proportions of dataquantities of the components of YCbCr422 image data are 1 each for Cbimage data and Cr image data against 2 of Y image data.

Reference numeral 1500 denotes image data inputted to the compressionprocessor 114. Reference numerals 1501, 1502 and 1503 respectivelydenote Y compressed image data (luminance-compressed image data), Cbcompressed image data (Cb chromatic difference-compressed image data)and Cr compressed image data (Cr chromatic difference-compressed imagedata), which are components of compressed image data generated bycompression of Y image data, Cb image data and Cr image data.

Because of the characteristic of human vision that is more sensitive toluminance (Y) components than to chromatic difference (Cb and Cr)components, it is possible to make the data quantity of compressed imagedata of Cb components (hereinafter referred to as Cb compressed imagedata) and the data quantity of compressed image data of Cr components(hereinafter referred to as Cr compressed image data) smaller than thedata quantity of compressed image data of Y components (hereinafterreferred to as Y compressed image data) by setting the compression rateof Y components higher than the compression rates of Cb components andCr components.

This embodiment represents one example of compression processing ofimage data higher in priority of transmission among different componentsof image data at a higher compression rate.

More specifically, the level of priority of Y compressed image datahigher in those of Cb compressed image data and Cr compressed image dataand, as the width of output bit from the data transmission section 115,12 bits are allocated to Y compressed image data, 6 bits to Cbcompressed image data, and 6 bits to Cr compressed image data.

When Y compressed image data 1501, Cb compressed image data 1502 and Crcompressed image data 1503 are to be outputted to TMDS channel 0 (8bits/cycle), TMDS channel 1 (8 bits/cycle) and TMDS channel 2 (8bits/cycle), respectively, the transmission bands occupied by thetransmitted compressed image data is limited to the TMDS channel 0 onwhich the compressed data quantity is the greatest, entailing elongationof the valid period.

Reference numerals 1505, 1506, 1507, 1508 and 1511 denote one example ofoutput data where more channels (12 bits/cycle) are allocated to Ycompressed image data than to Cb compressed image data (6 bits/cycle)and Cr compressed image data (6 bits/cycle). The use of this outputformula enables the valid period for transmitting compressed image datato be shortened.

To add, allocation of output bit width is instructed from the controller110 to the data transmission section 115. Or the data transmissionsection 115 may allocate in advance at predetermined rates ofdistribution according to an image format (for instance YCbCr444 or thelike) instructed from the controller. The rates of distribution may beset by the controller 115.

Whereas this embodiment has been described with respect to a case inwhich the image data are YCbCr444, for other image signals such as RGBsignal, too, the level of transmission priority may be given to eachindividual compressed image data set, and the bit width of outputting toan output transmission path (for instance TMDS channel 0, 1 or 2). Forexample where the image data is RGB signals, there is a method by whichthe level of transmission priority for G components can be set higherthan for the levels of transmission priority for R components and Bcomponents. More specifically, there is a method by which 12 bits areallocated as bit width of outputting to G components, and 6 bits eachare allocated as bit width of outputting to R components and Bcomponents.

Further, as another case of the level of transmission priority in whichthe image data are YCbCr444, there is a method by which a level oftransmission priority higher the other chromatic difference componentsis allocated to 4:2:2 components. More specifically, it is a method bywhich 20 bits are allocated as the output bit width for 4:2:2 and 4 bitseach are allocated as the output bit width for the remaining Cbcomponents and Cr components.

FIG. 38 shows another example of output waveforms in which inputted Ycompressed image data 1601 is outputted to the data transmission section115, and Cb compressed image data 1602 and Cr compressed image data 1603are outputted to TMDS channel 0, TMDS channel 1 and TMDS channel 2. Toadd, 1600 denotes image data to be input to the compression processor114.

Regarding this embodiment, a case in which bit 4, bit 5, bit 6 and bit 7of TMDS channel 0 and bit 0, bit 1, bit 6 and bit 7 of TMDS channel 1are lower in transmission error rate than other bits.

Reference numerals 1604, 1605, 1606, 1607, 1608 and 1609 denote examplesof output data where Y compressed image data is allocated to bits lowerin transmission error rate on TMDS channel. The use of this outputformula enables the error occurrence rate of Y compressed image data tobe brought down.

To add, in this embodiment Cb compressed image data is allocated to1602, 1605 and 1607, and Cr compressed image data is allocated to 1603and 1609.

Further, information on the transmission error rate is supplied from thecontroller 110 to the data transmission section 115. Or, on the basis ofthe transmission error rate, the controller may designate bit allocationof Y compressed image data, Cb compressed image data and Cr compressedimage data to TMDS channels. Although YCbCr luminance chromaticdifference signals have been taken up as an example in the descriptionof this embodiment, in other image forms including RGB signals as well,a level of priority may be assigned to each compressed image data set inbit allocation to TMDS channels.

Further, the level of transmission priority of each component may berepresented by the compression rate of each component. In this case, agreater output bit width shall be allocated to components of a highercompression rate and a smaller output bit width shall be allocated tocomponents of a lower compression rate. For instance, there is a methodby which the compression rates of different components (Y, Cb and Cr) ofYCbCr444 are respectively set to 80%, 40% and 40%, the levels oftransmission priority are respectively set to 2, 1 and 1, or anothermethod by which the output bit widths of different components (Y, Cb andCr) are respectively set to 12 bits, 6 bits and 6 bits.

Embodiment 3

Another mode of realizing the image transmission device and the imagereceiving device described as Embodiment 1 will be described below.

In this embodiment, main compression coding information is transmittedin a packet area in the horizontal blanking period 406 shown in FIG. 30.It does not take on a packet structure in spite of using the packetarea, and four-bit data are supposed to be transmitted on each channel.Further, auxiliary compression coding information 1740 is transmitted inthe valid period.

FIG. 39 shows one example of output data composition of the datatransmission section 115 when main compression coding information 1700is to be transmitted in the horizontal blanking period 406.

The use of this configuration can enhance error resistivity intransmitting the main compression coding information 1700 compared withtransmitting in the valid period. However, transmitting over atransmission path of a high transmission error rate poses a problem ofhow to further enhance error resistivity.

FIG. 40 shows one example in which main compression coding information1710, which is the same as the main compression coding information 1700,is to be transmitted in a horizontal blanking period over the sametransmission path. In this embodiment, the main compression codinginformation 1710 is outputted immediately after the main compressioncoding information 1700. To add, the main compression coding information1710 need not immediately follow the main compression coding information1700. The use of this configuration serves to enhance the redundancy ofthe main compression coding information, and makes it possible toprovide main compression coding information with high transmission errorresistivity even over a transmission path whose transmission error rateis high. To add, the redundancy level in this embodiment means thenumber of main compression coding information sets transmittedadditionally. In this embodiment, the redundancy level is supposed to be1.

FIG. 41 shows one example in which main compression coding information1720, which is the same as the main compression coding information 1700,is to be transmitted in a horizontal blanking period over a differenttransmission path. In this embodiment, a drop in transmission errorresistivity due to transmission error rate fluctuations from channel tochannel is restrained by transmitting the main compression codinginformation 1720 over a different channel than one for the maincompression coding information 1700.

For instance, if the transmission error rate on channel 0 is higher thanthe transmission error rate on channel 1, allocation of redundant maincompression coding information on channel 0 as shown in FIG. 40 wouldinvite a drop in error resistivity, but transmitting the same maincompression coding information sets over a plurality of channels asshown in FIG. 41 enables error occurrence rates of main compressioncoding information to be evened up. In this embodiment, two maincompression coding information sets allocated to each channel, but theymay as well be allocated to bit. For instance, there is a method toallocate the main compression coding information 1700 to bit 0 and bit 1of channel 0 and bit 0 and bit 1 of channel 1 and allocate the maincompression coding information 1700 to bit 2 and bit 3 of channel 0 andbit 2 and bit 3 of channel 1. Also, bit allocation may be changed inaccordance with information on the transmission error rate.

FIG. 42 shows an example in which the redundancy level is raised to 2from the embodiments shown in FIG. 40 and FIG. 41. The main compressioncoding information 1700 and main compression coding information 1730 andmain compression coding information 1731, both the same as the maincompression coding information 1700, are outputted.

The resistivity of the transmission path to errors may as well beenhanced by raising the redundancy level of main compression codinginformation according to the transmission error rate.

FIG. 43 shows a case in which the redundancy level is raised to 2 fromthe embodiments shown in FIG. 40 and FIG. 41. The main compressioncoding information 1700 and main compression coding information 1730 andmain compression coding information 1731, both the same as the maincompression coding information 1700, are outputted.

The redundancy level of main compression coding information may beraised according to the transmission error rate.

Whereas transmitting of redundant main compression coding informationwhen main compression coding information is to be transmitted in ahorizontal blanking period has been described so far, where auxiliarycompression coded images are to be transmitted in a valid period, theerror resistivity of auxiliary compression coding information may aswell be enhanced by transmitting redundant auxiliary compression codinginformation, which is the same as the auxiliary compression codinginformation, in a valid period.

FIG. 43 shows one example of output data composition of the datatransmission section 115 in a case in which, where auxiliary compressioncoding information is to be transmitted in a valid period, theredundancy level of the auxiliary compression coding information is setto 2.

The use of this configuration can strengthen error resistivity whenauxiliary compression coding information 1740 is to be transmitted.

The redundancy level of main compression coding information may as wellbe raised according to the transmission error rate.

Embodiment 4

In Embodiment 3, whereas the redundancy level of main compression codinginformation or auxiliary compression coding information is raisedaccording to the transmission error rate, there is a problem that thetransmission capacity of the transmission path over which additionalredundant compression coding information is to be transmitted islimited.

Therefore Embodiment 4 adopts a formula that allows an increase in thetransmission capacity of the transmission path over which redundantcompression coding information is to be transmitted by shortening thecompression rate or the compression formula and lengthening orshortening the horizontal blanking period according to the transmissionerror rate.

Instructions to increase/decrease the compression rate, compressionformula and horizontal blanking period and information on the redundancylevel of compression coding information are supplied from the controller110 to the compression processor 114 and the data transmission section115.

There is a method to convey by EIDI or CEC communication information onthe situation of responses on the image receiving device side toinstructions to increase/decrease the compression rate, compressionformula and horizontal blanking period and to the redundancy level ofcompression coding information from the image receiving device to theimage transmitting device.

Decisions regarding instructions to increase/decrease the compressionrate, compression formula and horizontal blanking period and theredundancy level of compression coding information in response to thetransmission error rate may be made either by the controller 110 orindividually by the compression processor 114 or the data transmissionsection 115.

FIG. 44 shows a case in which the transmission error rate is dividedinto three ranges and one example of compression rate, horizontalblanking period and redundancy level in each range. When a transmissionerror rate ER surpasses ERa (when the transmission error rate is high),the compression rate is set to 40%, the quantity of generated compressedimage data is reduced, the horizontal blanking period is shortened, andthe valid period is extended. The transmittable quantity of auxiliarycompression coding information to be transmitted in the valid period canbe thereby increased. In this embodiment, the resistivity of auxiliarycompression coding information to transmission errors is enhanced bysetting the redundancy level of auxiliary compression coding informationto 2 and transmitting two sets of redundant auxiliary compression codinginformation of the same contents as the auxiliary compression codinginformation in the valid period.

When the transmission error rate ER is at or below ERb (when thetransmission error rate is low), images of high picture quality are madetransmittable by setting the compression rate to 80% and increasing thequantity of generated compressed image data. The period in which no dataare transmitted is increased by refraining from insertion of redundantcompression coding information. The period in which no data istransmitted is the total of neither compressed image data nor auxiliarycompression coding information is transmitted in the valid period 406and neither packets nor main compression coding information istransmitted in the blanking period 407. Power saving is made possible bystopping the clock or taking actions at a frequency lower than the clockfrequency in this non-transmission period.

When the transmission error rate ER is above ERb but not above ERa (whenthe transmission error rate is normal), it is attempted not only toraise the transmission error resistivity but also to enhance the picturequality by setting the compression rate to 60% and the redundancy levelof auxiliary compression coding information to 1.

FIG. 45 shows a case in which the transmission error rate is dividedinto three ranges and another example of compression rate, horizontalblanking period and redundancy level in each range. When a transmissionerror rate ER surpasses ERa (when the transmission error rate is high),the compression rate is set to 40%, the quantity of generated compressedimage data is reduced, the horizontal blanking period is extended, andthe horizontal period is extended. The transmittable quantity of maincompression coding information to be transmitted in the horizontalblanking period can be thereby increased. In this embodiment, theresistivity of auxiliary compression coding information and maincompression coding information to transmission errors is enhanced bysetting the redundancy level of auxiliary compression coding informationto 1 and transmitting one set of redundant auxiliary compression codinginformation of the same contents as the auxiliary compression codinginformation in the valid period, setting the redundancy level of maincompression coding information to 1, and transmitting one set of maincompression coding information in the horizontal blanking period.

In addition, the compression rate described with reference to FIG. 44and FIG. 45, the compression formula may as well be altered. FIG. 46shows a case in which the transmission error rate is divided into threeranges and one example of compression formula, horizontal blankingperiod and redundancy level in each range. The compression formula ischanged over among formula A, formula B and formula C with thetransmission error rate ER. When the transmission error rate ER is aboveRa, resistivity to transmission errors can be enhanced by using acompression formula that involves less main compression codinginformation and can raise the redundancy level. Also, by applying acompression formula that can be expected to provide a high compressionrate (for instance the compression rate of 40% in FIG. 45), it is madepossible to increase the transmittable quantity of auxiliary compressioncoding information or main compression coding information.

Whereas the compression rate was taken up as an example in thedescription referring to FIG. 44 and FIG. 45, and the compressionformula was taken up in the description referring to FIG. 46, both thecompression rate and the compression formula may as well be switchedover according to the transmission error rate.

Although this embodiment has been described with reference to a case inwhich redundant main compression coding information or redundantauxiliary compression coding information is outputted to enhanceresistivity to transmission errors, the error coding formula may as wellbe switched over according to the transmission error rate. Or where thetransmission error rate is high, in addition to reducing the quantity ofcompressed image data after compression as shown in FIG. 45, resistivityto transmission errors can be enhanced by extending the horizontalblanking period and transmitting part of the auxiliary compressioncoding information in the horizontal blanking period.

With respect to this embodiment, a method to reduce compressed imagedata by processing compression at a low compression rate where thetransmission error rate is higher than a prescribed level, a method toreduce compressed image data by processing compression by using acompression formula suitable for a low compression rate, a method toincrease the transmission capacity of the transmission path for maincompression coding information by extending the horizontal blankingperiod, or a method to increase the transmission capacity of thetransmission path for auxiliary compression coding information byextending the valid period 406, but a method to reduce the number ofaudio packets transmitted in the horizontal blanking period by audiodata may be used as well. Examples of method to reduce audio datainclude a change from uncompressed audio form to compressed audio formand the number of audio channels from six to two.

Embodiment 5

Whereas the compression rate, horizontal blanking period and redundancylevel are increased according to the transmission error rate inEmbodiment 4, there is a problem that picture quality and errorresistivity in relation to the transmission error rate are determinedirrespective of the type of contents of image data. In this embodiment,picture quality and transmission error resistivity suitable for the typeof contents can be secured by altering the compression rate, horizontalblanking period and redundancy level according to the type of contents.To add, though the transmission error rate was not touched on in thedescription of this embodiment, this embodiment may further includeswitching over according to the transmission error rate.

FIG. 47 shows one example of formula to switch over the compressionrate, horizontal blanking period and redundancy level according to thetype of contents. In this embodiment, where the contents are acinematograph, the compression rate is set to 80%, the horizontalblanking period is extended, the redundancy level of main compressioncoding information is set to 2, and the redundancy level of auxiliarycompression coding information is set to 1 to enhance the picturequality and error resistivity. On the other hand, where the contents areJapanese checker/Japanese chess, error resistivity is enhanced byshortening the horizontal blanking period, setting the redundancy levelof main compression coding information to 1, and setting the redundancylevel of auxiliary compression coding information to 1 while thecompression rate is set to 40%, on account of the characteristic thatthere are many static parts.

Of where the contents are sports, it is considered that visualsensitivity to errors is low though the images involve many moving partsand are difficult to compress, the horizontal blanking period isshortened and the redundancy level of both main compression codinginformation and auxiliary compression coding information is set to 0,namely no redundant compression coding information is inserted whilesetting the compression rate to 80%, thereby to increasenon-transmission periods for data while seeking higher picture quality.

Embodiment 6

In Embodiment 4, where the transmission error rate is below itsprescribed level, picture quality enhancement was sought by increasingthe quantity of compressed image data at a high compression rate.Regarding this embodiment, one example of method to enhance soundquality when the transmission error rate is below its prescribed levelwill be described with reference to FIG. 48.

Reference numerals 1800 and 1802 denote the valid period 406 in whichcompressed image data or auxiliary compression coding information istransmitted, and 1801 denotes the blanking period 407 in which maincompression coding information or audio packets audio packets aretransmitted. Reference numeral 1810 denotes image data beforecompression. Reference numerals 1820, 1821 and 1822 concern one examplein which main compression coding information 1820 and an audio packet1821 are transmitted in a blanking period 1801 and auxiliary compressioncoding information or compressed image data 1822 are transmitted in avalid period 1802. In this case, the number of audio packetstransmittable within the blanking period 1801 is limited by thetransmitted quantity of the main compression coding information 1820.

Here, when the transmission error rate is below its prescribed level,main compression coding information 1830 may also be transmitted in thevalid period 1802. In this case, high sound quality can be achieved byallocating more audio packets to the blanking period.

Although error resistivity is higher in the blanking period than in thevalid period, the transmittable data quantity is ⅓ or less if thetransmission error rate is below its prescribed level.

FIG. 49 shows another example of formula to realize high sound quality.Reference numerals 1910, 1911 and 1912 concern one example oftransmitting main compression coding information 1910, audio packet1911, auxiliary compression coding information and compressed image data1912 when the valid period is not extended. In this example, there is novacancy in which the main compression coding information 1910 can betransmitted in the valid period.

Then, when the transmission error rate is below its prescribed level, aformula is chosen according to which the valid period is extended andmain compression coding information 1921 is transmitted in this extendedvalid period 1902. The main compression coding information 1921,auxiliary compression coding information and compressed image data 1922may be arranged anywhere if only it is within the extended valid period1902. In the case of this formula, since the transmittable data quantityin the valid period 1902 is three times that in the blanking period oreven more, the extended length of the valid period is 3/1 or less of thetransmission period of the main compression coding information in theblanking period. Therefore, as denoted by 1920, the blanking period inwhich audio packets can be transmitted can be extended. By increasingthe audio data quantity, sound quality can be enhanced. Examples ofsound quality enhancement features include an increased number ofchannels, audio signal generation at a higher sound frequency, audiosignal generation with larger quantized bits, and relaxation of bandlimitations in high and low ranges.

This embodiment so far described enables image data of a larger sizethan the currently prescribed image size to be transmitted over thecurrently prescribed transmission path by transmitting in a compressedform the image data to be transmitted by the image transmission device,and moreover it is possible to transmit compressed images having highererror resistivity by transmitting main compression coding information,which is part of compression coding information in an area made moreerror-resistive than the transmission area of image data.

Also, when image data of the currently prescribed image size is to betransmitted, the data transmission quantity per prescribed length oftime or the data transmission clock can be lowered, the frequency oferror occurrence can be brought down and, moreover, a system highlyreliable against errors on the transmission path can be architected.

Further, a system that can deal with errors in such a manner thatpicture quality deterioration due to an error is kept from beingconspicuous even if the error arises on the transmission path and theerror cannot be perfectly corrected.

REFERENCE SIGNS LIST

-   100 . . . Image transmission device-   101 . . . Input section-   102 . . . Input section-   103 . . . Input section-   104 . . . Input section-   105 . . . Tuner reception processor-   106 . . . Network reception processor-   107 . . . Recording medium controller-   108 . . . Recording medium-   109 . . . User IF-   110 . . . Controller-   111 . . . Stream controller-   112 . . . Decoder section-   113 . . . Display processor-   114 . . . Compression processor-   115 . . . Data transmission section-   116 . . . Output section-   191 . . . Data path-   192 . . . Data path-   193 . . . Data path-   200 . . . Image receiving device-   201 . . . Input section-   202 . . . Input section-   203 . . . User IF-   204 . . . Controller-   205 . . . Data reception processor-   206 . . . Expansion processor-   207 . . . Display processor-   208 . . . Display section-   300 . . . Cable

The invention claimed is:
 1. An image receiving device that divides a two-dimensional image including the number of horizontal valid pixels and the number of vertical valid lines into unit blocks smaller than the two-dimensional image and receives compressed image data compressed for each unit block, the image receiving device comprising: a receiving section that receives the compressed image data and horizontal size information of the unit block; an expansion processor that expands the compressed image data received by the receiving section and generates uncompressed image data; and a responding section that transmits performance information of the expansion processor in response to confirmation from an image transmission device which is a transmission source of the compressed image data, wherein the performance information includes horizontal size candidate information by which the compressed image data of the unit block is expandable, the receiving section receives the compressed image data on the basis of the horizontal size candidate information of the unit block from the image transmission device, and the expansion processor expands the compressed image data received by the receiving section in a valid period different from a blanking period on the basis of the horizontal size information of the unit block received by the receiving section in the blanking period, and generates the uncompressed image data.
 2. The image receiving device according to claim 1, wherein the performance information further includes vertical size candidate information by which the compressed image data of the unit block is expandable, the receiving section receives the compressed image data based on the vertical size candidate information of the unit block from the image transmission device, and the expansion processor expands the compressed image data received by the receiving section in a valid period different from a blanking period on the basis of the vertical size information of the unit block received by the receiving section in the blanking period, and generates the uncompressed image data. 